Ordinary printers are composed of a paper feeding unit and a paper ejecting or output unit that are connected to the front and back of one printing unit. The paper-ejecting unit may be connected to a post-processing device such as a sorter, a mailbox, or a finisher (electric stapler and/or puncher) on the exterior of the paper ejecting unit.
Recent printers are likely to have color printing or overlay printing of color and black and white printing in addition to black and white printing.
The prior printing units are color printing unit, black and white printing unit, and both color and black and white printing unit. If a color printer equipped with a color printing unit is a color ink jet printer, the printing speed to realize the highly accurate printing is approximately 1 to 10 pages per minute, or ppm, and it is reasonably priced. Black and white printers equipped with a black and white printing unit have the moderate printing speed of approximately 20 ppm to the high printing speed of over 40 ppm. Their prices are relatively high. Black and white and color printers equipped with both black and white and color-printing units have the printing speed of 1 to 10 ppm for color printing and the moderate printing speed of 20 ppm for black and white printing. The electric photograph method is expensive and has high capacity. The ink jet method is less expensive and has low capacity.
When color printing is applied to a sheet of paper along with black and white printing, ordinary technology required is to set up both black and white printer and color printer or one black and white and color printer.
When two printers, black and white printer and color printer, are set up, each printer has a set of a paper feeding means, a printing means, and a paper ejecting means, requiring high facility cost. The biggest problem is that it requires a large space in an office. When color printing is applied to a sheet of paper after black and white printing has been applied, the paper ejected from one printer needs to be manually carried over to the other printer to start printing. Therefore, efficiency of office administration is low.
And, in order to automatically process the printed cut papers with sorting, stapling, and punching a post processing machine needs to be connected to the exterior of the printer on the paper ejecting side. When the ordinary method of using two printers, a black and white printer and a color printer, is used, each printer is equipped with its own post processing machine, which increases facility cost and decreases usage efficiency of interior office space.
Furthermore, a black and white and color printer resolves the office space issue to a certain degree, but the printing speed is restricted to low speed for color printing and moderate speed for black and white printing. The biggest problem is its high cost.
As stated above, ordinary printers have problems in either or both facility cost and occupying space when black and white printing and color printing are administered.